StDev() and StDevP() Function in MS Access

1. StDev() Function :
StDev() Function in MS Access is used to estimate the standard deviation for a population sample.

Syntax :

StDev (expr)

Parameter : This method accept one parameter as mentioned above and described below :

• expr : It represents a string expression identifying the field that contains the numeric data which we want to evaluate or an expression that performs a calculation using the data in that field. Operands in expr can include the name of a table field, a constant, or a function.

Returns : It calculates standard deviation for a population sample.
Note : If the underlying query contains fewer than two records or no records then it returns a Null value which indicates that a standard deviation cannot be calculated.

Table – ProcuctDetails

Product_Id	Product_Price
100000	90
200001	81
298700	34
345632	84

Example1 :
The standard deviation for the product price.

SELECT stDev(Product_Price) AS StDEV_Value FROM ProcuctDetails;

Output :

StDEV_Value
25.7730479377197

Example2 :
The standard deviation for only one record.

SELECT stDev(100) AS StDEV_Value ;

Output :

StDEV_Value

So, we can see it cannot be calculated.


2. StDevP () Function :
StDevP() Function in MS Access is used to estimate the standard deviation for a population. The main difference between the StDevP() function and StDev() function is StDevP evaluates a population, and the StDev evaluates a population sample.

Syntax :

StDevP (expr)

Parameter : This method accept one parameter as mentioned above and described below :

• expr : It represents a string expression identifying the field that contains the numeric data which we want to evaluate or an expression that performs a calculation using the data in that field. Operands in expr can include the name of a table field, a constant, or a function.

Returns : It calculates standard deviation for a population.

Note : If the underlying query contains fewer than two records then it returns a Null value which indicates that a standard deviation cannot be calculated.

Table – Products

P_Id	P_Price
1001	55
1005	20
1008	66

Example-1 :

SELECT stDevP(P_Price) AS StDEVp_Value FROM Procucts;

Output :

StDEVp_Value
24.0208242989286

Example-2 :

SELECT stDevP(10) AS StDEVp_Value;

Output :

StDEVp_Value